I know this is an old question, but this is something I’ve hit upon myself and I think it might be a bug.
In my case, I have a skeletal mesh that is a weapon that moves around after an opponent. On collision, it attaches to the opponent - all working fine on the Host and if local, but never on a client.
What I discovered is that if your Skeletal Mesh is NOT the Root Component, then the network replication doesn’t work properly!
So as soon as I made the Skeletal Mesh the RootComponent, everything moved, attached and replicated correctly!
If anyone else stumbles across this - I think it might be a bug, unless some Epic staff could correct or provide some more information?